Molecular cloning and characterization of sea bass (Dicentrarchus labrax L.) CD8alpha

In this work, the gene and cDNA of the sea bass CD8alpha have been isolated and characterized. The coding sequence has an ORF of 666 bp. It retains the Ig motif that interacts with MHC and the two cysteines responsible for an intra-chain disulfide bridge. The hinge region contains the two essential cysteines involved in dimerization. The transmembrane region is well conserved in all analysed sequences. Similar to other teleosts, the cytoplasmic region lacks the consensus p56(lck) motif common in higher vertebrates. Analysis of the expression pattern using RT-PCR shows the highest expression in the thymus. Like in the human gene, the sea bass CD8alpha genomic structure is organized into six exons, which roughly correspond to separate functional domains of the protein. Southern blotting shows that CD8alpha exists as a single copy gene. Together, these results support the concept that the basic structure of CD8alpha has been maintained through evolution.     

Do surrogates describe patterns in marine macroalgal diversity in the Recherche Archipelago,temperate Australia?

• 1. Surrogates aim to predict species diversity and to minimize sampling effort. Here the value of surrogates for marine macroalgae is tested.
• 2. Higher taxonomic levels and dominant taxa were evaluated as surrogates for detecting patterns in macroalgal species diversity (derived from species‐level biomass data) in the Recherche Archipelago, Western Australia.
• 3. Data were stratified by two island groups (inshore and offshore), three depth intervals (<10 m, 10–20 m, >20 m), and two exposures to wave energy. Correlations between similarity matrices from surrogate and species diversity data matrices were analysed using a modified Spearman rank correlation (r_s). The ability of surrogates to detect differences between exposures to wave energy was also investigated using analysis of similarity. Species diversity data were aggregated to higher taxonomic levels and were either fourth‐root or presence/absence (richness) transformed.
• 4. Species richness was the most consistent surrogate (r_s‐values>0.69, P=0.001). Genus‐level richness was also strongly correlated to species diversity in the Recherche Archipelago, except in depths <10 m where patterns in diversity were characterized by species turnover.
• 5. At offshore islands in depths 10–20 m and >20 m, family‐ and order‐level biomass data were suitable surrogates owing to the abundance of Alariaceae (Order Laminariales) represented by a single genus and species. Surrogates using biomass data from the orders Laminariales, Ceramiales, Dictyotales and Fucales were also successful at offshore islands in middle to deeper depths.
• 6. At inshore islands in depths 10–20 m and >20 m, genera from the orders Gigartinales, Fucales and Ceramiales were strongly correlated to species biomass data.
• 7. Surrogates, like species richness, that were strongly correlated to species biomass data were also able to distinguish between exposures to wave energy, based on analysis of similarity tests.
• 8. Sampling effort would be reduced if collecting richness data in species‐rich macroalgal assemblages such as those found in temperate Australia.

Copyright © 2006 John Wiley & Sons, Ltd.     

Is the decline of birds and amphibians in a steppe lake of northern Patagonia a consequence of limnological changes following fish introduction?

• 1. Laguna Blanca, in Laguna Blanca National Park, is a lake in Patagonia which has been designated as a Ramsar site since 1971 because of bird diversity and abundance and importance for nesting, particularly for the black neck swan, Cygnus melanocoryphus. It is also valued for its populations of endemic amphibians, Atelognathus patagonicus and Atelognathus praebasalticus.
• 2. Avian and amphibian populations have decreased dramatically in recent years. Percichthys colhuapiensis, Percichthys trucha (Pisces, Percichthyidae), Salmo trutta and Oncorhynchus mykiss (Pisces, Salmonidae) were introduced into Laguna Blanca in 1965. Since 1986, no Atelognathus frogs have been found. The abundance of swans and coots, which are strongly associated with macrophytes for nesting and feeding, has diminished drastically, whereas piscivorous birds have increased.
• 3. The fishless condition of some neighbouring small lakes with abundant pond weeds, aquatic birds and endemic amphibians, was assessed in order to compare the physical and chemical characteristics and the quantitative composition of the benthos among lakes. Fish presence at Laguna Blanca and its absence at El Burro, Antiñir and Jabón lakes, were confirmed. Compared with previous results, it seems that the abundance of Amphipoda (Hyalella), Copepoda and Cladocera at Laguna Blanca has decreased, while Acari has increased and Notostraca has disappeared. Water transparency has diminished in Laguna Blanca and now is lower than that of fishless lakes.
• 4. P. colhuapiensis were captured only in Laguna Blanca, with the highest captures in the littoral zone. The population shows rapid individual growth in the early years and an absence of fish older than 6 years. The preponderance of benthos and the presence of macrophytes in the gut contents of adult P. colhuapiensis appear to indicate that they are important consumers of these resources.
• 5. This paper concludes that fish introduction in Laguna Blanca led to a complex trophic cascade effect (fish predation on tadpoles, fish competition for avian food, bottom disturbance, zooplankton reduction) producing deleterious effects on the amphibian and bird populations.

Copyright © 2006 John Wiley & Sons, Ltd.     

Adenosine deaminase activity in serum, erythrocytes and lymphocytes of rats infected with Leptospira icterohaemorrhagiae

Leptospirosis is a systemic disease of humans and domestic animals, mainly dogs, cattle and swine. The course of human leptospirosis varies from mild to severe fatal forms and the most severe form of human leptospirosis is principally caused by Leptospira interrogans serovar icterohaemorrhagiae (L. icterohaemorrhagiae). The enzyme adenosine deaminase (ADA) plays an important role in the production and differentiation of blood cells. The aim of this study was to evaluate the activity of ADA in serum, erythrocytes and lymphocytes of rats infected with L. icterohaemorrhagiae, as compared with non-infected rats. Twenty-four adult rats, divided into two uniform groups (A and B) were used for the enzymatic assays. The animals in Group B were inoculated intraperitoneally with 2×10(8) leptospires/rat, and the rodents in Group A (control) were not-inoculated. Blood collection was performed on days 5 and 15 post-infection (PI) and the blood used to assess the ADA activity. The infection by L.icterohaemorrhagiae altered erythrocyte count, hemoglobin concentration and hematocrit, causing a decrease in all these parameters on day 15 PI. Lymphocytes decreased significantly on day 15 PI, and ADA activity in serum was inhibited in infected rats on days 5 and 15 PI and its activity in erythrocytes were increased on day 5 PI. On day 5 PI, we found an increase in ADA activity in erythrocytes of infected rats. No correlation was observed between hematocrit and erythrocyte ADA activity on days 5 and 15 PI. The ADA activity was inhibited in rats infected on day 15 PI. A positive correlation (r(2)=60) was also observed between the number of lymphocytes and ADA activity in lymphocytes on day 15 PI (P<0.05). In conclusion, our results showed that the ADA activity is altered in serum, lymphocytes and erythrocytes in experimental infection by L.icterohaemorrhagiae in rats, concomitantly with hematological parameters.